Coated microbubbles for treating an aquifer or soil formations

ABSTRACT

A microporous diffuser includes a first elongated member including at least one sidewall having a plurality of microscopic openings. The sidewall defines an interior hollow portion of the member. The diffuser has a second elongated member having a second sidewall having a plurality of microscopic openings, the second member being disposed through the hollow region of the first member. The diffuser includes an end cap to seal a first end of the microporous diffuser and an inlet cap disposed at a second end of microporous diffuser for receiving inlet fittings.

This application is a divisional application of application Ser. No.10/910,441 filed on Aug. 2, 2004 now U.S. Pat. No. 6,984,329, which wasa continuation of application Ser. No. 10/354,584 filed Jan. 30, 2003(now U.S. Pat. No. 6,780,329), which was a divisional of applicationSer. No. 10/223,166 filed on Aug. 19, 2002 (U.S. Pat. No. 6,596,161),which was a continuation of application Ser. No. 09/470,167, filed Dec.22, 1999 (U.S. Pat. No. 6,436,285).

BACKGROUND

This invention relates generally to water remediation systems.

There is a well recognized need to clean-up contaminants that exist inground and surface water. In particular, there is one type ofcontamination problem which widely exists, that is, the contamination ofsurface waters or subsurface waters which find their way to the surfacesuch as, for example, in a contaminated spring. Such surface waters maybe contaminated with various constituents including volatilehydrocarbons, such as chlorinated hydrocarbons including trichloroethene(TCE), tetrachloroethene (PCE).

SUMMARY

According to an additional aspect of the present invention, amicroporous diffuser includes a first elongated member including atleast one sidewall having a plurality of microscopic openings, saidsidewall defining an interior hollow portion of said member and a secondelongated member having a second sidewall having a plurality ofmicroscopic openings, said second member being disposed through thehollow region of said first member. The diffuser includes an end cap toseal a first end of the microporous diffuser and an inlet cap disposedat a second end of microporous diffuser for receiving inlet fittings.

According to an additional aspect of the present invention, amicroporous diffuser includes a first hollow cylindrical tube having asidewall comprising a plurality of microscopic openings and a secondhollow tube having a sidewall having a plurality of microscopicopenings, said second tube being disposed through said first tube. Thediffuser also includes an end cap to seal ends of said tubes and aninlet cap disposed to provide inlets to interior portions formed bysidewalls of said tubes.

According to a still further aspect of the invention, a microporousdiffuser includes a first hollow cylindrical tube coupled to a firstinlet and adapted to be fed by a gas, the tube having a sidewallcomprising a plurality of microscopic openings the openings having adiameter in a range of 1 to 200 microns and a second hollow tube coupledto a second inlet and adapted to be fed by a liquid, the tube having asidewall with a plurality of microscopic openings, the openings having adiameter in a range of 1 to 200 microns, with the first tube beingdisposed through the second tube and arranged such that gas injectedinto the first tube travels towards the sidewall of the second tubeforming microfine bubbles laminated with the liquid. The diffuser alsoincludes an end cap to seal first ends of the tubes and an inlet capdisposed to seal second ends of said tubes and to support the first andsecond inlets to the interior portions formed between the tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical view of a typical surface water treatmentexample.

FIG. 2 is a block diagram of an apparatus used in the treatment process.

FIGS. 3A and 3B are respectively plan and elevational views somewhatschematic, of a spring box used in the apparatus of FIG. 2.

FIGS. 3C and 3D are plan and elevational views of still alternate springbox arrangements.

FIGS. 4A and 4B are longitudinal cross-section and plan cross-sectionalviews of a microporous diffuser useful in the spring box of FIGS. 3A and3B;

FIGS. 5A, 5B are longitudinal cross-section and plan cross-sectionalviews, respectively, of an alternative microporous diffuser useful inthe spring box of FIGS. 3A and 3B.

FIGS. 6A and 6B are cross-sectional view of sidewalls of the microporousdiffusers of either FIGS. 4A, 4B or 5A, 5B showing exemplaryconstruction details.

FIGS. 7A, 7B are longitudinal cross-section and plan cross-sectionalviews, respectively, of a still alternative microporous diffuser usefulin the spring box of FIGS. 3A-3D.

FIGS. 8A and 8B are respectively plan and elevational views somewhatschematic, of a circular spring box arrangement with a mixing featurealso useful in the apparatus of FIG. 2.

FIG. 9 is a cross-sectional view showing an alternative treatmentexample.

FIG. 10 is a plot of removal rate of PCE for an aqueous solutionequivalent to 120 ppb, over differing bubble sizes.

DETAILED DESCRIPTION

Referring now to FIG. 1, an example 10 of the use of an apparatus fortreatment of surface water or in-situ removal of contaminants from wateris shown. Illustrated in FIG. 1 is a site 11, having a subsurfaceaquifer 14 that produces surface waters 12 such as by a spring. Aspring-box treatment system 20 disposed on the site 11. The spring boxtreatment system 20 is disposed to intercept the surface water 12 and todivert the surface water into the spring box treatment system 20 toremove contaminants such as volatile hydrocarbons and, in particular,chlorinated hydrocarbons which may exist in the water in the aquifer 14.The spring box treatment system 20 outputs a water stream 16 which issubstantially free of the contaminants.

Contaminants which can be treated or removed by use of the spring boxtreatment system 20 include hydrocarbons and, in particular, volatilechlorinated hydrocarbons such as tetrachloroethene, trichloroethene,cisdichloroethene, transdichloroethene, 1-1-dichloroethene and vinylchloride. In particular, other materials can also be removed from thestream including chloroalkanes, including 1,1,1 trichloroethane, 1,1,dichloroethane, methylene chloride, and chloroform; benzene, toluene,ethylbenzene, O-xylene, P-xylene, naphthalene and methyltetrabutylether(MTBE). It should be understood that the use of the spring-box treatmentsystem 20 is not limited to flowing surface water but could be used totreat pumped or stored water.

Referring now to FIG. 2, the spring box treatment system 20 includes aspring box 30, and an air compressor 22, a compressor/pump controlmechanism 24, and an ozone (O₃) generator 26. The air compressor 24 canfeed a stream of air into the spring box 30 whereas, the compressor pumpcontrol 24 feeds a stream of air mixed with ozone (O₃) from the ozonegenerator 26 into the spring box 30 to affect substantial removal of theabove-mentioned or similar types of contaminants. Optionally, or inaddition thereto, the apparatus 20 can also include a pump 28 thatsupplies a liquid decontamination agent such as hydrogen peroxide orcatalyst agents including iron containing compounds such as ironsilicates or palladium or palladized carbon. To promote biodegradationreactions, the liquid introduced can be a nutrient mixture of nitrogen(ammonium or nitrate), phosphorus, and potassium along with oxygen as agas to promote oxic reactions or carbon dioxide and hydrogen sulfide topromote reduction reactions.

The spring box 30 uses primarily a gas-gas reaction between contaminantvapors and ozone (described below). This reaction can be supplementedwith a liquid phase reaction. A liquid decontaminator such as hydrogenperoxide can also be used. The use of hydrogen peroxide as a thin filmcoating on the bubbles promotes the decomposition rate by adding asecondary liquid phase reactive interface as volatile compounds enterthe gaseous phase. It also expands the types of compounds that can beeffectively removed. Alternatively, the pump control 28 can simply feedwater.

Referring now to FIGS. 3A and 3B, an arrangement of a spring box 30 isshown. The spring box includes a container 31 comprised of a sidewall 32of a durable material such as concrete over which is disposed orattached a water tight lid 33 also comprised of concrete. Within thespring box 30 is provided an inlet port 42 to receive the water from thespring, as well as a plurality of partially closed chambers 40 a-40 dwhich are formed within the interior of the spring box by walls orpartitions 38 a-38 c. Within each of the chambers 40 a-40 d are disposeda plurality of microporous diffusers such as those shown in conjunctionwith my issued U.S. Pat. No. 5,855,775 which is incorporated herein byreference. Alternatively, microporous diffusers 50, 70, as describedbelow in conjunction with FIGS. 4A and 4B or FIGS. 5A and 5B may beused.

In the arrangement shown in FIG. 3A, a first pair of microporousdiffusers 50 a, 50 b or 70 a, 70 b are coupled to a common gas/liquidfeed arrangement 36 a which can be fed, for example, fromcompressor/pump 24 and compressor 28 (FIG. 2). The spring box 30 alsoincludes a second feed arrangement 38 b which in this embodiment has oneof the microporous diffusers 50 c, 70 c being fed with a combination ofair, ozone and air, ozone and liquid as above, and with the secondmicroporous diffuser 50 d, 70 d being fed only by air to provide airstripping of any residual ozone before exiting of the treated water.

As shown in FIG. 3B, the microporous diffusers are arranged in elevationabove the bottom of the spring box 30 within a pool 39 of water providedfrom the spring or other surface water source.

FIGS. 3C and 3D show still alternate spring box arrangements. In thearrangement 30′ of FIG. 3C, the diffusers 50 or 70 are coupled in serieswhereas FIG. 3D shows diffusers 50, 70 arranged to be staggered inelevation over the height of the spring box.

The spring box 30 is an ozone reactor vessel in which ozone is pumpedinto the pool of water through the use of the microporous diffusers. Themicroporous diffusers are disposed in the water under treatment andtransfer ozone into the water in the form of microfine or fine bubbleswhich promote rapid gas/gas/water reactions with volatile organiccompounds particularly in the presence of a catalyst or enhancer whichmay participate in the gaseous phase of the reaction, instead of solelyenhancing dissolved aqueous disassociation and reactions. In addition,with the optional use of the liquid port to the apparatus, the gas/gasreactions are optimized to include gas/gas reactions within the gaseousphase as well as inducing water aqueous phased reactions to achieve anoverall decomposition rate within the gaseous phase and the aqueousphase from second water reactions. For example, the use of hydrogenperoxide as a laminate coating on the bubbles can enhance decompositionrates as mentioned below. The micron plastic bubblers may also be coatedwith or have sintered into construction an outer layer of activatedcarbon or activated carbon with palladium to simultaneously accumulateand promote decomposition of the chloroethenes.

The production of microbubbles and selection of appropriate sizedistribution are selected for optimized gas exchange through highsurface area to volume ratio and long residence time within the liquidto be treated. The microbubbles are generated by using microporousmaterials in the microporous diffuser 50 that acts as a bubble chamber,as shown in the embodiment 50 (FIG. 4A-4B) or, alternatively, throughthe embodiment 70 of the microporous diffuser of FIG. 5A-5B. Theapparatus 20 promotes the continuous production of microbubblesminimizing coalescing or adhesion. The injected air/liquid combinationmoves as a fluid into the water to be treated; whereas,microencapsulated ozone within the microfine bubbles enhances andpromoted in-situ stripping of volatile organics and simultaneouslyterminates normal reversible Henry

s reaction.

Referring now to FIGS. 4A-4B, a microporous diffuser 50 is shown. Themicroporous diffuser 50 includes a first cylindrical member 56 comprisedof a hydrophobic material which provides an outer cylindrical shell forthe microporous diffuser 50. The cylindrical member 56 has a sidewall 56a which is comprised of a large plurality of micropores. A secondcylindrical member 60 is coaxially disposed within the first cylindricalmember 56. The second cylindrical member 60 is comprised of ahydrophobic material and has a sidewall 60 a which is comprised of alarge plurality of micropores. Also disposed within the confines of thefirst cylindrical member 56 are a plurality of cylindrical members 58,here four, which have sidewalls 58 a having a large plurality ofmicropores and also comprised of a hydrophobic material.

A proximate end of central cylindrical member 60 is coupled to a firstinlet port 52 a which is provided from a first inlet cap 52 andproximate ends of the plurality of cylindrical members 58 are coupled tosecond inlet ports generally denoted as 52 b. At the opposite end of themicroporous diffuser 50 an end cap 54 covers distal ends of cylindricalmembers 56 and 60. Here distal ends of the plurality of cylindricalmembers 58 are sealed by separate caps 59 but could be terminated by theend cap 54. The end cap 54 in conjunction with cap 52 seals the distalends of the microporous diffuser. Each of the cylindrical members 56, 58and 60 are here cylindrical in shape and have a plurality of microscopicopenings constructed through sidewalls 56 a, 58 a and 60 a,respectively, thereof having pore sizes matched to or to create a poresize effective for inducing gas/gas reactions in the spring box 30.Sidewalls of each of the cylindrical members can have a pore diameter ina range of 1-200 microns, preferably 1-50 microns and more preferably5-20 microns. The combination of the inlet cap 52 and end cap 54 sealsthe microporus diffuser 50 permitting liquid and gas to escape by theporous construction of sidewalls of the microporous diffusers.

The microporous diffuser 50 can be filled with a microporous materialsuch as microbeads with mesh sizes from 20 to 200 mesh or sand pack orporous hydrophilic plastic to allow introducing a liquid into the porespaces where liquid is exiting.

Referring now to FIGS. 5A and 5B, an alternate embodiment 70 of amicroporous diffuser is shown. The microporous diffuser 70 includes anouter cylindrical member 76 having a sidewall 76 a within which isdisposed an inner cylindrical member 78 having a sidewall 78 a. Theinner cylindrical member 78 is spaced from the sidewall of the outercylindrical member. The space 77 between the inner and outer cylindricalmembers 76, 78 is filled with a packing material comprised of glassbeads or silica particles (silicon dioxide) or porous plastic which, ingeneral, are hydrophilic in nature. This space is coupled to an inputport 72 b which receives liquid, and catalysts, and/or nutrients frompump 39 (FIG. 2). The microporous diffuser 70 has the inner cylindricalmember 78 disposed coaxial or concentric to cylindrical member 78.Sidewalls of each of the cylindrical members can have a pore diameter ina range of 1-200 microns, preferably 1-50 microns and more preferably5-20 microns. A proximate end of the inner cylindrical member is coupledto an inlet port 72 a which is fed an air ozone mixture from pump 36.The microporous diffuser also includes an end cap 74 which incombination secures distal ends of the cylinders 76 and 78. Thecombination of the inlet cap 72 and end cap 74 seals the microporusdiffuser permitting liquid and gas to escape by the porous constructionof sidewalls of the microporous diffusers.

Referring now to FIGS. 6A, 6B, construction details for the elongatedcylindrical members for the microporous diffusers 50, 70 are shown. Asshown in FIG. 6A, sidewalls of the members can be constructed from ametal or a plastic support layer 91 having large (as shown) or fineperforations 91 a over which is disposed a layer of a sintered i.e.,heat fused microscopic particles of plastic. The plastic can be anyhydrophobic material such as polyvinylchloride, polypropylene,polyethylene, polytetrafluoroethylene, high density polyethylene (HDPE)and ABS. The support layer 91 can have fine or coarse openings and canbe of other types of materials. FIG. 6B shows an alternative arrangement94 in which sidewalls of the members are formed of a sintered i.e., heatfused microscopic particles of plastic. The plastic can be anyhydrophobic material such as polyvinylchloride, polypropylene,polyethylene, polytetrafluoroethylene, high density polyethylene (HDPE)and alkylbenzylsulfonate (ABS).

The fittings (i.e., the inlets in FIGS. 4A, 5A can be threaded and areattached to the inlet cap members by epoxy, heat fusion, solvent orwelding with heat treatment to remove volatile solvents or otherapproaches. Standard threading can be used for example NPT (nationalpipe thread) or box thread e.g., (F480). The fittings thus are securelyattached to the microporous diffusers in a manner that insures that themicroporous diffusers can handle pressures that are encountered withinjecting of the air/ozone and liquid.

Referring to FIGS. 7A-7B, an alternate microporous diffuser 90 is shown.The microporous diffuser 90 includes a first cylindrical member 96comprised of a hydrophobic material which provides an outer cylindricalshell for the microporous diffuser 90. The cylindrical member 96 has asidewall 96 a that is comprised of a large plurality of micro pores. Aproximate end of cylindrical member 96 is coupled to a first inlet port92 a provided from a first inlet cap 92 and a distal end of thecylindrical member 96 is coupled to an end cap 94 The end cap 94 inconjunction with cap 92 seals the ends of the microporous diffuser 90.Sidewalls of the cylindrical members 96 is provided with a film of acatalysts or reaction promoter or and absorbing material. Examplesinclude a layer 93 of activated carbon that is abraded into the surfaceor sintered into the surface. Additionally palladized activated carboncould also be used. As explained above the layer 93 can aid indecomposition of the contaminants in the water. Sidewalls of each of thecylindrical members can have a pore diameter in a range of 1-200microns, preferably 1-50 microns and more preferably 5-20 microns.

The use of catalysts supported by absorptive materials such aspalladized activated carbon can be particularly effective for compoundsthat have an absorptive affinity to activated carbon. The compounds suchas TCE are concentrated near the release location of the ozone microbubbles, allowing more efficient reaction for water containing lowerconcentrations of TCE as explained above. The layer 93 can also beprovided on the other embodiments 50, 70 above, e.g., on either or bothcylindrical members but preferably on the members that deliver the ozoneto the water.

Referring now to FIGS. 8A and 8B, an alternate arrangement of a springbox 110 is shown. The spring box 110 includes a circular container 111comprised of a sidewall 112 of a durable material such as concrete overwhich is disposed or attached a water tight lid 113 also comprised ofconcrete. Within the spring box 110 is provided an inlet port 115 a toreceive the water from the spring. Within the circular container aredisposed a plurality of microporous diffusers such as those shown inconjunction with my issued U.S. Pat. No. 5,855,775 which is incorporatedherein by reference. Alternatively, microporous diffusers 50, 70, 90, asdescribed above in conjunction with FIGS. 4A and 4B, FIGS. 5A and 5B, orFIGS. 7A-7B may be used.

In the arrangement shown in FIG. 8A, the microporous diffusers 116 arecoupled to a common rotary joint 117 that can provides a gas/ozone feedarrangement 86 a which can be fed, for example, from compressor/pump 24and compressor 28 (FIG. 2).

As shown in FIG. 8B, the microporous diffusers are arranged in elevationabove the bottom of the spring box 110 within a pool 119 of waterprovided from the spring or other surface water source. The rotary joint117 enables the microporous diffusers to be rotated in the waterenabling the ozone to more effectively mix with the water. The springbox 110 can include a sand or other matrix 120 containing a reactionpromoter e.g., catalyst as mentioned.

The spring box 110 is an ozone reactor vessel in which ozone is pumpedinto the pool of water through the use of the microporous diffusers. Themicroporous diffusers 116 are disposed in the water under treatment andtransfer ozone into the water in the form of micro fine or fine bubbleswhich promote rapid gas/gas/water reactions with volatile organiccompounds particularly in the presence of a catalyst or enhancer whichmay participate in the gaseous phase of the reaction, instead of solelyenhancing dissolved aqueous disassociation and reactions.

In addition, an optional liquid port (not shown) to the rotary joint canbe provided to include gas/gas reactions within the gaseous phase aswell as inducing water aqueous phased reactions to achieve an overalldecomposition rate within the gaseous phase and the aqueous phase fromsecond water reactions. For example, the use of hydrogen peroxide as alaminate coating on the bubbles can enhance decomposition rates asmentioned above.

Referring now to FIG. 9, an alternative example of the use of themicroporous diffusers 50, 70 is shown. The example shows an injectionwell to treat subsurface waters of an aquifer. The arrangement includesa well having a casing with an inlet screen and outlet screen to promotea recirculation of water into the casing and through the surroundingground area. The casing supports the ground about the well. Disposedthrough the casing is microporous diffusers e.g., 50 or 70. Theinjection well treatment system 120 also includes an air compressor 132,a compressor/pump control mechanism 134, and an ozone (O₃) generator136. The air compressor 134 can feed a stream of air into themicroporous diffuser 50 whereas, the compressor pump control 134 feeds astream of air mixed with ozone (O₃) from the ozone generator 136 intomicroporous diffuser to affect substantial removal of theabove-mentioned or similar types of contaminants. Optionally, or inaddition thereto, the treatment system 120 can also include a pump 138that supplies a liquid decontamination agent such as hydrogen peroxideas well as nutrients and catalyst agents including iron containingcompounds such as iron silicates or palladium containing compounds suchas palladized carbon. In addition, other materials such as platinum mayalso be used.

The treatment system 120 makes use of a gas-gas reaction of contaminantvapors and ozone (described below) that can be supplemented with aliquid phase reaction. The use of hydrogen peroxide as a thin filmcoating on the bubbles promotes the decomposition rate by adding asecondary liquid phase reactive interface as volatile compounds enterthe gaseous phase. It also expands the types of compounds that can beeffectively removed. Alternatively, the pump control 138 can simply feedwater.

In particular, with the microporous diffusers 50 and 70 and use of theoptional port to introduce a liquid such as hydrogen peroxide or waterinto the chamber, the microbubbles are produced in the microporousdiffuser by bubbling air/ozone through the central cylinder of themicroporous diffusers and into the surrounding outer regions of themicroporous diffusers. At the same time, a liquid is introduced into themicroporous diffusers 50, 70 and laminates an outer surface of bubblesformed by the gas. The liquid forms a liquid barrier between the waterto be treated and the inside gas containing air/ozone. This arrangementthus can be injected into a slurry containing a catalyst such assilicate, iron silicate, palladium, palladized carbon or titaniumdioxide to produce rapid reactions to decompose contaminants within thepool of water contained in the spring box 30. The reactions can proceedas set out below.

The process uses microfine bubble injection to produce simultaneousextraction/decomposition reactions as opposed to simply creating smallerand smaller sized bubbles for the purpose of injecting into free water.The process involves generation of fine bubbles which can promote rapidgas/gas/water reactions with volatile organic compounds which asubstrate (catalyst or enhancer) participates in, instead of solelyenhancing dissolved (aqueous) disassociation and reactions. Theproduction of microbubbles and selection of appropriate sizedistribution is provided by using microporous material and a bubblechamber for optimizing gaseous exchange through high surface area tovolume ratio and long residence time within the liquid to be treated.The equipment promotes the continuous production of microbubbles whileminimizing coalescing or adhesion.

The injected air/liquid combination moves as a fluid into the water tobe treated. The use of microencapsulated ozone enhances and promotesin-situ stripping of volatile organics and simultaneously terminates thenormal reversible Henry

s reaction. The process involves promoting simultaneous volatile organiccompounds (VOC) in-situ stripping and gaseous decomposition, withmoisture (water) and substrate (catalyst or enhancer). The reactionmechanism is not a dissolved aqueous reaction. In some cases, with cis-or trans-DCE, the aqueous phase reaction may assist the predominantlygas-phase reaction.

The remote process controller and monitor allows for the capability forsensor feedback and remote communication to the pump control 24 andozone (or oxygen or both) generator 26 to achieve a certain level ofgaseous content (e.g., dissolved oxygen, ozone, or other gas) and rateof mixing to promote efficient reactions. This is done by sensors 39(FIGS. 3A, 3B) placed in the bubble chambers at certain distances fromthe microporous diffusers 50, 70. Oxygen content, redox potential, anddissolved VOC concentration of the water can be monitored within thetreatment system. The operator can access the information, modifyoperations and diagnose the condition of the unit by telephone modem orsatellite cell phone. This provides on-site process evaluation andadjustment without the need of on-site operator presence.

Appropriately sized microfine bubbles can be generated in a continuousor pulsing manner which allows alternating water/bubble/water/bubblefluid flow. The microfine bubbles substantially accelerate the transferrate of volatile organic compounds like PCE from aqueous to gaseousstate. Reducing the size of the bubbles to microfine sizes, e.g., 5 to50 microns, can boost extraction rates. These sizes boost exchange ratesand do not tend to retard rise time by too small a size. When anoxidizing gas (ozone) is added into the microbubbles, the rate ofextraction is enhanced further by maintaining a low interior(intrabubble) concentration of PCE, while simultaneously degrading thePCE by a gas/gas/water reaction. The combination of both processesacting simultaneously provides a unique rapid removal system which isidentified by a logarithmic rate of removal of PCE, and a characteristicratio of efficiency quite different from dissolved (aqueous) ozonereactions. The compounds commonly treated are HVOCs (halogenatedvolatile organic compounds), PCE, TCE, DCE, vinyl chloride (VC),petroleum compounds (BTEX: benzene, toluene, ethylbenzene, xylenes).

An analysis of the reaction mechanism is set out. Gaseous exchange isproportional to available surface area. With partial pressures andmixtures of volatile gases being held constant, a halving of the radiusof bubbles would quadruple (i.e., times) the exchange rate. If, in thebest case, a standard well screen creates air bubbles 200 times the sizeof a medium sand porosity, a microporous diffuser of 5 to 20 micron sizecreates a bubble 1/10 the diameter and six to ten times thevolume/surface ratio as shown in Table 1.

TABLE 1 Diameter Surface Area Volume Surface Area/ (microns) 4π 4/3 πVolume 200 124600 4186666 0.03 20 1256 4186 0.3

Theoretically, the microporous bubbles exhibit an exchange rate of tentimes the rate of a comparable bubble from a standard ten slot wellscreen.

TABLE 2 Surface to Volume (A/V) Ratio Changes As Function of Bubble SizeAs Bubble Volume Increases D (i.e.,2r) or h as Fraction of Pore Size 0.10.25 0.5 1 2 5 10 20 Sphere SPHERIOD Area = 4 πr² 0.0314 0.19625 0.7853.14 18.8 37.7 69 131 Vol = 4/3 πr³ 0.0005 0.00817 0.065 0.53 6.3 15.731 62 Ratio 62 24 12 5.9 3 2.4 2.2 2.1

In wastewater treatment, the rate of transfer between gas and liquidphases is generally proportional to the surface area of contact and thedifference between the existing concentration and the equilibriumconcentration of the gas in solution. Simply stated, if the surface tovolume ratio of contact is increased, the rate of exchange alsoincreases as illustrated in Table 2. If, the gas (VOC) entering thebubble (or micropore space bounded by a liquid film), is consumed, thedifference is maintained at a higher entry rate than if the VOC isallowed to reach saturation equilibrium. In the case of a halogenatedvolatile organic carbon compound (HVOC), PCE, gas/gas reaction of PCE toby-products of HCl, CO₂ and H₂O accomplishes this. In the case ofpetroleum products like BTEX (benzene, toluene, ethylbenzene, andxylenes), the benzene entering the bubbles reacts to decompose to CO₂and H₂O. The normal equation for the two-film theory of gas transfer is:r _(m) =K _(g) A(C _(g) −C)where:

-   -   r_(m)=rate of mass transfer    -   K_(g)=coefficient of diffusion for gas    -   A=area through which gas is diffusing    -   C_(g)=saturation concentration of gas in solution    -   C=concentration of gas in solution.

The restatement of the equation to consider the inward transfer of phasechange from dissolved HVOC to gaseous HVOC in the inside of the bubblewould be:

-   -   C_(S)=Saturation concentration of gas phase of HVOC or VOC in        bubble.    -   C=Initial concentration of gaseous phase of HVOC or VOC in        bubble volume.

Soil vapor concentrations are related to two governing systems: waterphase and (non-aqueous) product phase. Henry

s and Raoult

s Laws are commonly used to understand equilibrium-vaporconcentrations-governing volatilisation from liquids. When soils aremoist, the relative volatility is dependent upon Henry

s Law. Under normal conditions (free from product) where volatileorganic carbons (VOCs) are relatively low, an equilibrium of soil,water, and air is assumed to exist. The compound tetrachloroethene (PCE)has a high exchange capacity from dissolved form to gaseous form. If thesurface/volume ratio is modified at least ten fold, the rate of removalshould be accelerated substantially.

FIG. 10 shows a plot of removal rate of PCE for an aqueous solutionequivalent to 120 ppb, over differing bubble sizes. The air volume andwater volume is held constant. The only change is the diameter ofbubbles passed through the liquid from air released from a diffuser.

Ozone is an effective oxidant used for the breakdown of organiccompounds in water treatment. The major problem in effectiveness is thatozone has a short lifetime. If ozone is mixed with sewage containingwater above ground, the half-life is normally minutes. Ozone reactsquantitatively with PCE to yield breakdown products of hydrochloricacid, carbon dioxide, and water.

To offset the short life span, the ozone is injected with microporousdiffusers, enhancing the selectiveness of action of the ozone. Byencapsulating the ozone in fine bubbles, the bubbles wouldpreferentially extract volatile compounds like PCE from the mixtures ofsoluble organic compounds they encountered. With this process, volatileorganics are selectively pulled into the fine air bubbles. Gas enteringa small bubble of volume (4πr³) increases until reaching an asymptoticvalue of saturation. If we consider the surface of the bubble to be amembrane, a first order equation can be written for the monomolecularreaction of the first order. The reaction can be

$\frac{\mathbb{d}x}{\mathbb{d}t} = {K\left( {Q - X} \right)}$written as follows:

-   where X is the time varying concentration of the substance in the    bubble, Q is the external concentration of the substance, and K is    the absorption constant.    X=Q(l−e ^(Kt))

If at time t=0, X=0, then:

$K = \frac{{\mathbb{d}x}/{\mathbb{d}t}}{Q - X}$

The constant K is found to be:

By multiplying both numerator and denominator by V, the

$K = \frac{v\;{{\mathbb{d}x}/{\mathbb{d}t}}}{v\left( {Q - X} \right)}$volume of the bubble, we obtainwhich is the ratio between the amount of substance entering the givenvolume per unit time and quantity V(Q−X) needed to reach the asymptoticvalue. By analyzing the concentration change within the fine bubblessent through a porous matrix with saturated (water filled) solutioninteracting with the matrix (sand), and determining the rate ofdecomposition of the products (TCE+ozone=CO₂+HCl) and(Benzene+ozone=CO₂+HOH), the kinetic rates of reaction can becharacterized.

The rate which the quantity k₁QV of the substance flows in one unit oftime from aqueous solution into the bubble is proportional to Henry

s Constant. This second rate of decomposition within the bubble can beconsidered as k₁, a second

$\frac{\mathbb{d}x}{\mathbb{d}t} = {{k_{l}Q} - {k_{2}X}}$rate of reaction (−k₂X), where

$X = {\frac{k_{1}}{k_{2}}Q}$and, at equilibrium, as dx/dt=0, gives

However, if the reaction to decompose is very rapid, so −k₂X goes tozero, the rate of reaction would maximize k₁Q, i.e., be proportional toHenry

s Constant and maximize the rate of extraction since VOC saturation isnot occurring within the bubbles.

The combination of microbubble extraction and ozone degradation can begeneralized to predict the volatile organic compounds amenable to rapidremoval. The efficiency of extraction is directly proportional to Henry

s Constant. Multiplying the Henry

s Constant (the partitioning of VOCs from water to gas phase) times thereactivity rate constant of ozone for a particular VOC yields the rateof decomposition expected by the microbubble process.

The concentration of HVOC expected in the bubble is a consequence ofrate of invasion and rate of removal. In practice, the ozoneconcentration is adjusted to yield 0r _(voc)=−K_(L) a _(voc)(C−C _(L))concentration at the time of arrival at the surface.

-   -   where:    -   f_(voc)=rate of VOC mass transfer, (μg/ft³        h)    -   (K₁a)_(voc)=overall VOC mass transfer coefficient, (1/h)    -   C=concentration of VOC in liquid    -   C_(L)=saturation concentration of VOC in liquid μg/ft³ (μg/m³)

The saturation concentration of a VOC in wastewater is a function of thepartial pressure of the VOC in the atmosphere in contact with thewastewater.

${\frac{c_{g}}{C_{L}} = {H_{c}\mspace{14mu}{thus}}},{C_{g} = {H_{C} \cdot C_{L}}}$

-   -   C_(g)=concentration of VOC in gas phase μg/ft³ (μg/m³)    -   C_(L)=saturation concentration of VOC in liquid μg/ft³ (μg/m³)    -   H_(c)=Henry        s Constant

The rate of decomposition of an organic compound C_(g) (when present ata concentration (C) by ozone can be formulated

${{- \left( \frac{\mathbb{d}C_{g}}{\mathbb{d}t} \right)}O_{3}} = {{K_{oc}\left( O_{3} \right)}\left( C_{g} \right)}$by the equation:

-   or, after integration for the case of a batch reactor:

$\begin{matrix}{{{- \ln}\left( \frac{\; C_{\; g_{\;{end}}}}{\; C_{\; g_{\; o}}} \right)} = {{K_{\; o_{\; c}}\left( O_{\; 3} \right)}t}} & \left( {{equation}\mspace{14mu} 2} \right) \\{\left( C_{g} \right)_{end} = {C_{o}{e_{o\; c}^{- K}\left( O_{3} \right)}t}} & \; \\{\frac{\left( C_{g} \right)_{end}}{\left( C_{g} \right)_{o}} = {{e_{o_{c}}\left( O_{3} \right)}t}} & \;\end{matrix}$where

-   (O₃)=concentration of ozone averaged over the reaction time (t)-   (C_(g))_(o)=halocarbon initial concentration-   (C_(g))_(end) =halocarbon final concentration    Substituting:-   rm=K_(g)A (C_(g)−C) From Henry    s Law:-   rm=K_(g)A ((H_(g)·C_(g)) C)−C_(g)=H_(c)·C_(g) (equation 3)-   rm=K_(g)Z ((H_(g)·C_(g))−C) With ozone

$\begin{matrix}{{rm} = {{{K_{g}{Z\left( {\left( {H_{c} \cdot C_{g}} \right) - C - {{K_{o}\left( O_{3} \right)}\left( C_{g} \right)}} \right)}\left( {{Hg} \cdot C} \right)} - {{K_{o}\left( O_{3} \right)}\left( C_{g} \right)}} = 0}} & \left( {{equation}\mspace{14mu} 4} \right)\end{matrix}$Rate of decomposition is now adjusted to equal the total HVOC enteringthe bubble.SET: (H _(c) ·C _(g))=Ko(O ₃) (C _(g))  (equation 5)therefore surface concentration=0

This condition speeds up the rate of extraction because the VOC neverreaches equilibrium or saturation in the bubble.

Table 4 gives the Henry

s Constants (H_(c)) for a selected number of organic compounds and thesecond rate constants (R₂) for the ozone radical rate of reaction insolely aqueous reactions where superoxide and hydroxide reactionsdominate. The third column presents rates of removal process.

TABLE 4 REMOVAL RATE COEFFICIENTS Ozone Aqueous Second Order Rate RateRemoval Organic Constant (a.) Henry□s Coefficient Compound (M⁻¹ SEC⁻¹ )Constant (b.) (τ) (c.) Benzene 2 5.59 × 10³ 0.06 Toluene 14 6.37 × 10³0.07 Chlorobenzene 0.75 3.72 × 10³ 0.013 Dichloroethylene 110 7.60 × 10³0.035 Trichloroethylene 17 9.10 × 10³ 0.05 Tetrachloroethylene 0.1 25.9× 10³ 0.06 Ethanol 0.02  .04 × 10³ 0.0008 (a.) From Hoigne and Bader,1983. □Rate of Constants of Direct Reactions of Ozone with Organic andInorganic Compounds in Water-I. Nondissociating Compounds□ Water Res/17: 173-184. (b.) From EPA 540/1-86/060, Superfund Public HealthEvaluation Manual EPA 540/1-86/060 (OSWER Directive 9285.4-1) Office ofEmergency and Remedial Response, Office of Solid Waste and EmergencyResponse. (c.) See U.S. Pat. No. 5,855,775.

The rapid removal rate of this process does not follow Hoigne and Bader(1983) rate constants. However, there is a close correlation to Henry

s Constant as would be expected from equation 5. The presence of thesubstrate (sand) and moisture is necessary to complete the reaction. Theactive ingredient in the sand matrix appears to be an iron silicate. Thebreakdown products include CO₂ and dilute HCl.

Two sets of equations are involved in the reactions:

Dissolved Halogenated Compounds

Dissolved Petroleum Distillates

Exemplary compounds are normally unsaturated (double bond), halogenatedcompounds like PCE, TCE, DCE, Vinyl Chloride, EDB; or aromatic ringcompounds like benzene derivatives (benzene, toluene, ethylbenzene,xylenes). Also, pseudo Criegee reactions with the substrate and ozoneappear effective in reducing certain saturated olefins like trichloroalkanes (1,1,-TCA), carbon tetrachloride (CCl₄), chloroform andchlorobenzene, for instance.

The following characteristics of the contaminants appear desirable forreaction:

Henry□s Constant: 10⁻² to 10⁻⁴ m³ · atm/mol Solubility: 10 to 20,000mg/l Vapor pressure: 1 to 3000 mmhg Saturation concentration: 5 to 9000g/m³

Absorption-Destruction

Absorptive substrates like activated carbon and certain resins serve toremove disolved volatile organic carbon compounds by absorption to thesurface. The active surface of particles contain sites which thecompounds attach to. The surface absorption is usually mathematicallymodeled by use of a Langmuir or Freunlich set of equations forparticular sizes of particles or total surface area if the material ispresented in cylinders or successive plates.

The derivation of the Langmuir isotherm stipulated a limited number ofabsorption sites on the surface of the solid. The absorption of a soluteon the surface necessitates the removal of a solvent molecule. Anequilibrium is then reached between the absorbed fraction and theremaining concentration in solution. If a continual gas phase ofmicrobubbles is being released from a porous surface, can remove theabsorbed molecule and decompose it, the reaction would be moved alongmuch faster than in aqueous phase without the collecting surface.

$Q_{l} = \frac{K_{L\; 1}C_{L\; 1}}{1 + {K_{L\; 1}C_{L\; 1}}}$

-   Q₁=fractional surface coverage of solute-   K_(L1)=equilibrium constant-   C_(L1)=solute concentration

1. A method comprises: forming microbubbles including an oxidizing gasentrapped by water and having a coating of hydrogen peroxide over themicrobubbles to provide microbubbles including the oxidizing gas havingthe hydrogen peroxide coating to treat contaminants.
 2. The method ofclaim 1 wherein the microporous bubbles are introduced using amicroporous diffuser.
 3. The method of claim 2 wherein the microporousdiffuser includes a nutrient agent and/or a catalyst agent to contactand become carried by the microbubbles.
 4. The method of claim 1 whereinthe microbubbles have a diameter of less than 200 microns.
 5. The methodof claim 1 wherein oxidizing gas is ozone.
 6. The method of claim 1wherein oxidizing gas is oxygen.
 7. The method of claim 1 wherein theoxidizing gas includes ozone and air in the microbubbles with the ozone.8. The method claim 1 wherein forming the microbubbles comprises:introducing an air-ozone stream through a first plurality of centrallydisposed members, having sidewalls of microporous material; andintroducing a liquid including hydrogen peroxide through a space betweenthe first plurality of centrally disposed members and a second memberthat surrounds the first plurality of centrally disposed members, andwhich is in fluid communication with the first plurality of centrallydisposed members, to coat surfaces of microbubbles entrapping air-ozoneexiting the first plurality of centrally disposed members with a coatingof the hydrogen peroxide.
 9. The method claim 1 wherein forming themicrobubbles comprises: introducing an air-ozone stream through a firstcentrally disposed member, having sidewalls of a microporous material;and introducing a liquid including hydrogen peroxide through a spacebetween the first centrally disposed member and a second member thatsurrounds the first centrally disposed member, and which is in fluidcommunication with the first centrally disposed member, the first andsecond members disposed in a wet soil formation, and the first member toproduce microbubbles entrapping air-ozone and the second member to coatsurfaces of the microbubbles with a coating of the hydrogen peroxide.10. The method of claim 1 wherein the microbubbles have a diameterwithin a range of about 1-50 microns.
 11. The method of claim 1 whereinthe microbubbles have a diameter in a range of about 5-20 microns. 12.The method of claim 9 wherein the space between the first and secondmembers is filled with a hydrophilic packing material.
 13. The method ofclaim 9 wherein space between the first and second members is filledwith a packing material comprised of glass beads, silica particles orporous plastic, and receives the hydrogen peroxide.
 14. A methodcomprises: forming microbubbles of an oxidizing gas with themicrobubbles having a coating of hydrogen peroxide by introducing theoxidizing gas through a microporous diffuser disposed in contact withwater; and contacting the microbubbles with the hydrogen peroxide. 15.The method of claim 14 wherein the microporous diffuser includes anutrient agent and/or a catalyst agent to contact and become carried bythe microbubbles.
 16. The method of claim 14 wherein the microbubbleshave a diameter of less than 200 microns.
 17. The method of claim 14wherein the oxidizing gas is ozone.
 18. The method of claim 14 whereinoxidizing gas is oxygen.
 19. The method of claim 14 wherein theoxidizing gas includes ozone, and included in the microbubbles with theozone is air.
 20. The method claim 14 wherein forming the microbubblescomprises: introducing an air-ozone stream through the microporousdiffuser, the microporous diffuser having a first, centrally disposedmember with sidewalls comprised of a microporous material, and a secondmember that surrounds the first, centrally disposed member and which isin fluid communication with the first, centrally disposed member; andintroducing a liquid including hydrogen peroxide through a space betweenthe first centrally disposed member and the second member, with thefirst and second members disposed in a wet soil formation, with thefirst member to produce microbubbles entrapping air-ozone, and thesecond member to coat surfaces of the microbubbles with the coating ofthe hydrogen peroxide.
 21. The method claim 14 wherein forming themicrobubbles comprises: introducing an air-ozone stream through a firstplurality of centrally disposed members, having sidewalls of microporousmaterial; and introducing a liquid including hydrogen peroxide through aspace between the first plurality of centrally disposed members and asecond member that surrounds the first plurality of centrally disposedmembers, and which is in fluid communication with the first plurality ofcentrally disposed members, to coat surfaces of microbubbles entrappingair-ozone exiting the first plurality of centrally disposed members witha coating of the hydrogen peroxide.